Autumn and Winter

[Big Bear]

I agree - no correlation at all. I mean- did a this years cold March 'ruin' the summer? I think not! A pleasent, warm September (and even October) will have NO bearing on snowy episodes in winter.

Yup.

You're always going to get patterns, even from rolling dice. Matching them really is dancing with the devil and has about as much (or less) use as folklore.

[beng]

Looking forward to the Met Office forecast issued this Thursday. I expect their NAO predictions to mirror those at UCL and backing down from their original strongly positive anomoly suggestion, although still favouring mild.

Hi Big Bear

Just a quick correction - the MO forecast is for a weakly positive NAO based on their Sea Temperature anomoly technique:

http://www.met-office.gov.uk/research/seas.../nao/index.html - I would agree that Scandi blocking looks likely this winter unless patterns radically change in the next month or so (always possible of course) - although we obviously need the block to extend far enough West - or we face quite a mild Southerly flow - this will likely depend on the jet strength and direction during Jan/Feb.

Ben

[BLAST FROM THE PAST]

All is gearing up for an 'interesting' winter. I suspect that overall the winter temps will come in as just above longterm average or spot on average. It is interesting to see yet again that the LPs 'still' cannot cross the UK and stall. NE blocking looks a good bet with the earlier appearnce of the great Russian HP as Roger has alluded to. Potential for a very active jet but with a more active southern arm? Crossing the big pond it is expected that a wetter and colder than average winter is expected for the Carolinas which for me adds to the spice as this suggests a southerly jet kicking out of the US.

BFTP

[Big Bear]

Thanks Ben & Ian

What do we need to look for with regards to precursors/ suggestions that high latitude blocking may occur in the days leading up to such an event??

Are there any obvious hallmarks in pressure patterns or weather changes that lead to HP situated to our north & east??

Thanks again

BB

That question also directed to BFTP or anyone else..

[Cheviot]

I just noticed that the press are beginning to mention the possibility of an El Nino event for 2006/ 2007.

http://news.bbc.co.uk/1/hi/sci/tech/5345184.stm

El Nino events are associated with reduced hurricane activity in the Carribean and higher rainfall in Northern Europe. Assuming the early indicators are correct, that an El Nino event is beginning, then we can look forward to more rainfall. I'm not sure if El Nino winters are statistically milder, but I suspect this may be the case based on memory.

So, may be our best chance of a decent snowfall will be generated by cold pooling over Siberia/ Scandanavia extending towards the UK, the warm Atlantic maritime or Polar maritime air colliding with this somewhere over the UK leading to an occluded front and heavy snow; this type of event lead to the heavy snows in 1947, though I'm uncertain whether this was an El Nino year. In other words, it's business as usual this Winter!

[BLAST FROM THE PAST]

I just noticed that the press are beginning to mention the possibility of an El Nino event for 2006/ 2007.

http://news.bbc.co.uk/1/hi/sci/tech/5345184.stm

El Nino events are associated with reduced hurricane activity in the Carribean and higher rainfall in Northern Europe. Assuming the early indicators are correct, that an El Nino event is beginning, then we can look forward to more rainfall. I'm not sure if El Nino winters are statistically milder, but I suspect this may be the case based on memory.

So, may be our best chance of a decent snowfall will be generated by cold pooling over Siberia/ Scandanavia extending towards the UK, the warm Atlantic maritime or Polar maritime air colliding with this somewhere over the UK leading to an occluded front and heavy snow; this type of event lead to the heavy snows in 1947, though I'm uncertain whether this was an El Nino year. In other words, it's business as usual this Winter!

Mild to Moderate EL NINO at best/worst. I don't think it has bad impact on the UK. It will be interesting to see how it develops and how the Atlantic responds...

BFTP

[summer blizzard]

Don't know if this has been spotted already - but hey!

http://forecast.mssl.ucl.ac.uk/docs/NAO200...6%20-%202007%22

Thanks for that Shuggee, last year they went for a slightly negative NAO, so while still wrong, they were the closest in terms of the NAO forecast.

Cheers Shugs. I'll have a read of that later

I've also been noticing something about our recent pattern from mid-late September. We have a high pressure dominance (which is influencing, rather than being our weather).

This high pressure is a fluctuation from Scandi to Euro High. At the moment this is holding well.

Any suggestions what this could mean for further months? Well, I suppose one suggestion would depend on how much Euro and Scandi cool over Autumn, but an interesting spot?

I have also noticed that as well, i believe that is due to the linkup of high pressure between Greenland and Europe, resulting in them finding a midle ground over Scandinavia, this is also causing low pressure to try and undercut the block however due to the relative strength of the European High, the low pressure ends up stalling.

At least the current setup is allowing continued cold air buildup.

All is gearing up for an 'interesting' winter. I suspect that overall the winter temps will come in as just above longterm average or spot on average. It is interesting to see yet again that the LPs 'still' cannot cross the UK and stall. NE blocking looks a good bet with the earlier appearnce of the great Russian HP as Roger has alluded to. Potential for a very active jet but with a more active southern arm? Crossing the big pond it is expected that a wetter and colder than average winter is expected for the Carolinas which for me adds to the spice as this suggests a southerly jet kicking out of the US.

BFTP

Yes, this suggests a positive PNA pattern which is supported by the positive PDO and EPO expected by me this winter.

For those of you that believe that that a warm September/Cold October increases the chances of a warmer than average winter, read the previous winter thread, it clearly shows a slight bias towards cold.

Edited September 18, 2006 by summer blizzard

[North-Easterly Blast]

What actually was the NAO index for the winter 2005-06? I do not know myself. I know they predicted negative NAO last year, but was it?

I see that the UKMO are predicting slightly positive this year, which does not imply a 1997-98 mild rout disaster, or even 2001-02, does it? I would say that even with a weakly positive NAO it may still be possible to get something as good as perhaps 2000-01.

[BLAST FROM THE PAST]

What actually was the NAO index for the winter 2005-06? I do not know myself. I know they predicted negative NAO last year, but was it?

I see that the UKMO are predicting slightly positive this year, which does not imply a 1997-98 mild rout disaster, or even 2001-02, does it? I would say that even with a weakly positive NAO it may still be possible to get something as good as perhaps 2000-01.

There was great debate in Spring. I think it was not a negative NAO but more on the neutral side. Even with negative NAO you can still get blocking in wrong place bringing mildish temps and also with slightly positive cold spells and right setups do occur .

An abrupt transition to recurring positive phases of the NAO occurred during the 1979/80 winter, with the atmosphere remaining locked into this mode through to the 1994/95 winter season. During this 15-year interval, a substantial negative phase of the pattern appeared only twice, in the winters of 1984/85 and 1985/ 86. However, November 1995 - February 1996 (NDJF 95/96) was characterized by a return to the strong negative phase of the NAO. Halpert and Bell (1997; their section 3.3) recently documented the conditions accompanying this transition to the negative phase of the NAO.

What is of note is that the winter of 86/87 with the great Jan of 87 was in the period of recurring positive phases. So neutral/slightly positive is nowt to concern about

BFTP

Edited September 18, 2006 by BLAST FROM THE PAST

[North-Easterly Blast]

I would hardly call December 2001 a very cold month. Yes it was below average but it was not notably so, it was certainly not a patch on Dec 1995. Dec 2001 was reasonably good for recent years in its cold spell it featured in the final ten days with severe frosts at times and some snow in parts of the UK, but the rest of the month wasn't up to much, a rather mild start followed by two weeks of anticyclonic non-descript weather.

[summer blizzard]

The overall NAO value for the winter was 0.1, so neutral however both December and February observed weakly negative NAO conditions, so the overall value was offset by an positive NAO January.

[Dawlish]

I remember it as slightly positive too, SB, but the graph that the Met Office uses is so difficult to read as to be almost hopeless.

http://www.met-office.gov.uk/research/seas.../nao/index.html

The graph should be a bar graph, as these are 2 discrete variables for each year ie observed and expected NAO. These are not changes over time and should therefore not be described with a line graph. It makes accurate comparisons almost impossible. From this graph, it looks to me, as if the NAO was -0.4, but that was not the case, I'm sure. It was very slightly positive, as SB, and I, remember and the outcome NAO lay outside the error bars (95% confidence limits, or 2 standard deviations) that you can see drawn on the 2006 forecast i.e. statistically thay did not get their NAO forecast right, though their actual winter forecast (which takes the NAO forecast into account, but the outcome of which is not directly dependent on it, as BFTP rightly explains) was very good.

It is hard to understand why the Met Office chooses a line graph format, for displaying the NAO over time. They shouldn't and it is confusing. The bottom scale complounds this - you really struggle to see the individual years. There would be no such problem if they used a bar graph with 2 different colours to represent observed and expected. If any of my "A" level students had used a line graph to represent a non-time dependent variable, they'd have been shot!

Paul

Edited September 18, 2006 by Dawlish

[Weather-history]

Winter 1978-79 was an unusual winter in that not only was it notably cold but it was also notably "wet". The winter of 1978-79 is actually the 13th "wettest" winter on record. I suspect its the only winter with a CET that is less than 2C to be in the top 50 wettest winters on record.

As I suspected, you have to go down to the 90th wettest winter to find the next sub 2C winter, 1878-79.

[Thundery wintry showers]

In general, as Ian Brown mentioned above, we need northern blocking to deliver anything significant/sustained to the British Isles. I think this applies to both northerly and easterly sources.

Northerlies:

I think for northerlies, for them to be sustainable or keep recurring, you need extensive blocking to the north-west, and by this I don't mean a flimsy little Greenland High, I mean a pronounced anticyclone like this:

http://www.wetterzentrale.de/archive/ra/20...00120001227.gif

A flimsy little Greenland High with a northerly tracking jet usually gets pushed out of the way:

http://www.wetterzentrale.de/archive/ra/20...00120031221.gif

http://www.wetterzentrale.de/archive/ra/20...00120031222.gif

Easterlies:

For easterlies to deliver, ideally you need there to have been a recent northerly blast in the near-Continent, pumping cold air south. This suggests northern blocking- a high somewhere to the N or NE of Britain pumps cold air south on its eastern flank and then directs it westwards towards Britain.

http://www.wetterzentrale.de/archive/ra/19...00119910203.gif

http://www.wetterzentrale.de/archive/ra/19...00119910207.gif

It's also possible to have a good easterly from the same kind of blocking that brings potent northerlies- a Greenland High which throws up a ridge towards Scandinavia:

http://www.wetterzentrale.de/archive/ra/19...00119820106.gif

On the other hand, easterlies aren't much use when the blocking gets no further NW than southern Scandinavia:

http://www.wetterzentrale.de/archive/ra/20...00120021209.gif

http://www.wetterzentrale.de/archive/ra/20...00120060122.gif

Zonality:

From what I've seen, for snowy incursions from the W and NW you need either a Greenland High pumping cold air into the mid-Atlantic that then "returns" eastwards, or less commonly, air from a pronounced Alaskan/Canadian cold pool across the Atlantic over to Britain. In either case a generally southerly tracking jet but with lowest pressure to the N and NE is generally paramount:

http://www.wetterzentrale.de/archive/ra/19...00119840115.gif

http://www.wetterzentrale.de/archive/ra/19...00119950302.gif

If you don't have a cold enough source or long enough track over the Atlantic, you end up with only localised, marginal snow events:

http://www.wetterzentrale.de/archive/ra/19...00119880208.gif

Just some pointers for those looking ahead to next winter.

[Nick F]

I remember it as slightly positive too, SB, but the graph that the Met Office uses is so difficult to read as to be almost hopeless.

http://www.met-office.gov.uk/research/seas.../nao/index.html

The graph should be a bar graph, as these are 2 discrete variables for each year ie observed and expected NAO. These are not changes over time and should therefore not be described with a line graph. It makes accurate comparisons almost impossible. From this graph, it looks to me, as if the NAO was -0.4, but that was not the case, I'm sure. It was very slightly positive, as SB, and I, remember and the outcome NAO lay outside the error bars (95% confidence limits, or 2 standard deviations) that you can see drawn on the 2006 forecast i.e. statistically thay did not get their NAO forecast right, though their actual winter forecast (which takes the NAO forecast into account, but the outcome of which is not directly dependent on it, as BFTP rightly explains) was very good.

Well, the NAO indices for DJF were as follows:

Dec 2005: -0.4

Jan 2006: 1.3

Feb 2006: -0.5

Source CPC: http://www.cpc.noaa.gov/products/analysis_...etin/table3.jpg

So makes DJF NAO 2005/06 +0.13

This was the Met Office 2005/06 winter weather summary back on 3rd March this year talking about how their forecast went:

http://www.metoffice.com/corporate/pressof...r20060303b.html

Correct me if I'm wrong but I'm sure their NAO outcome for the last winter season suggests negative, unless perhaps they use different indices to the CPC ones.

[Dawlish]

Well, the NAO indices for DJF were as follows:

Dec 2005: -0.4

Jan 2006: 1.3

Feb 2006: -0.5

Source CPC: http://www.cpc.noaa.gov/products/analysis_...etin/table3.jpg

So makes DJF NAO 2005/06 +0.13

This was the Met Office 2005/06 winter weather summary back on 3rd March this year talking about how their forecast went:

http://www.metoffice.com/corporate/pressof...r20060303b.html

Correct me if I'm wrong but I'm sure their NAO outcome for the last winter season suggests negative, unless perhaps they use different indices to the CPC ones.

Well there's strange Nick. I distinctly remember, up until the NAO forecast for this winter was produced, that the graph I referred to earlier showed the error bars and a slightly positive, winter 2006, NAO lying just outside them! Funny how the memory plays tricks!

Edited September 18, 2006 by Dawlish

[Big Bear]

Thanks TWS for all those pointers towards blocking scenarios.

My fingers are crossed for 1991 style easterly. I know the chances are slim but the way recent winters have been I'd take a northerly outbreak at any chance.

BB

[Turnedoutniceagain]

In general, as Ian Brown mentioned above, we need northern blocking to deliver anything significant/sustained to the British Isles. I think this applies to both northerly and easterly sources.

Northerlies:

I think for northerlies, for them to be sustainable or keep recurring, you need extensive blocking to the north-west, and by this I don't mean a flimsy little Greenland High, I mean a pronounced anticyclone like this:

http://www.wetterzentrale.de/archive/ra/20...00120001227.gif

A flimsy little Greenland High with a northerly tracking jet usually gets pushed out of the way:

http://www.wetterzentrale.de/archive/ra/20...00120031221.gif

http://www.wetterzentrale.de/archive/ra/20...00120031222.gif

Easterlies:

For easterlies to deliver, ideally you need there to have been a recent northerly blast in the near-Continent, pumping cold air south. This suggests northern blocking- a high somewhere to the N or NE of Britain pumps cold air south on its eastern flank and then directs it westwards towards Britain.

http://www.wetterzentrale.de/archive/ra/19...00119910203.gif

http://www.wetterzentrale.de/archive/ra/19...00119910207.gif

It's also possible to have a good easterly from the same kind of blocking that brings potent northerlies- a Greenland High which throws up a ridge towards Scandinavia:

http://www.wetterzentrale.de/archive/ra/19...00119820106.gif

On the other hand, easterlies aren't much use when the blocking gets no further NW than southern Scandinavia:

http://www.wetterzentrale.de/archive/ra/20...00120021209.gif

http://www.wetterzentrale.de/archive/ra/20...00120060122.gif

Zonality:

From what I've seen, for snowy incursions from the W and NW you need either a Greenland High pumping cold air into the mid-Atlantic that then "returns" eastwards, or less commonly, air from a pronounced Alaskan/Canadian cold pool across the Atlantic over to Britain. In either case a generally southerly tracking jet but with lowest pressure to the N and NE is generally paramount:

http://www.wetterzentrale.de/archive/ra/19...00119840115.gif

http://www.wetterzentrale.de/archive/ra/19...00119950302.gif

If you don't have a cold enough source or long enough track over the Atlantic, you end up with only localised, marginal snow events:

http://www.wetterzentrale.de/archive/ra/19...00119880208.gif

Just some pointers for those looking ahead to next winter.

Excellent info' TWS, I'll save this.

Here's hoping **sigh**

[Damien]

***ECPC dynamic winter forecast***

If you remember a few weeks ago we were discussing the very interesting if very questionable ECPC output with that phenomenal chart showing most of the Northern Hemisphere as below normal for the coming December:

complete with a nice easterly "warm (or rather in this case "warmer") patch" type set-up just above the UK in the G-I-N corridor.

I've not yet seen the current ECPC "short-range" charts (which would now go into early January BTW), but I was hoping that the ECPC "dynamic" would back up their current forecast of serious cold for the NH in December. And it does... ... of sorts:

These charts show a well above normal November and December (or a O-N-D and N-D-J period to be more exact) but a slightly above average or close to normal January and February (D-J-F and J-F-M period respectively). So a 2000/01-type winter possibly from that, only with January slightly cooler than December minus GW. A mild end to 2006 as a year though for most of us. A colder than average winter beginning in November for the Eastern United States... again. A small El Niño too.

It should also be noted that the southern tip of Greenland is above normal... again. This is an interesting point to note as far as the Jet stream is concerned.

These charts have consistently shown a mild winter for some months now, and now - at this critical moment in this critical month for winter - they are showing a more "normal" or "slightly above average" winter.

Overall I would say that those charts show what is closer to a slightly over average than normal winter due to Western and even Central Europe being also slightly above average, the cold (which is in itself not that intense this year looking at those charts albeit just slightly below average for those regions nonetheless) never really leaving Eastern Europe, esp. the ancient Muscovy region.

I see that the UKMO are predicting slightly positive this year, which does not imply a 1997-98 mild rout disaster, or even 2001-02, does it? I would say that even with a weakly positive NAO it may still be possible to get something as good as perhaps 2000-01.

Or even 1990/91, which was also a recent (in meteorological terms) "weakly positive" NAO winter.

Edited September 18, 2006 by Damien

[Dawlish]

Nice one Damien; no new thread for this!

So, mild or cold. Probably one, or the other.

Paul

[The Enforcer]

I just noticed that the press are beginning to mention the possibility of an El Nino event for 2006/ 2007.

http://news.bbc.co.uk/1/hi/sci/tech/5345184.stm

Well that almost cetainly means there won't be an El Nino now as those dimwits always get it wrong. Scorching August anyone?

What is of note is that the winter of 86/87 with the great Jan of 87 was in the period of recurring positive phases. So neutral/slightly positive is nowt to concern about

Perhaps you are onto something there. Maybe this winter needs to take the form of regular interchanges between pressure patterns - the transitional phases would be where the snow may come. Too many recent winters have been dominated by one type (Bartlett/Stagnant High/Weak Easterly).

I know the chances are slim but the way recent winters have been I'd take a northerly outbreak at any chance.

You'd need to move about 300 miles further north.

[Damien]

So, mild or cold. Probably one, or the other.

The forecast is for neither, with the exception of December (the N-D-J period). The forecast is for a slightly above average or close to average winter post-December, probably more the former due to the evident mildness forecast in Europe at this time.

personally, i expect a rather average December and January, followed by a very cold February.

How can you back up your assertion for a "very cold February" when:

1. Most forecast models (i.e.: TWOs, the French MetO.'s, and I think they may be another) are forecasting a rather strong "mild or very mild" (I believe) signal for February?,

2. Our winters have been a lot milder of late, like the last one?

However, I do agree that February along with perhaps slightly more prominently December has also shown a slight "cooling trend" over our recent winters since about 2003. An exceptionally mild February would indeed certainly break this trend, as would this rumoured "very cold" January. Even if it was just one "stand-out" cold spell like January 1987 in an otherwise mild month CET wise (which would still be possible if we had very mild south and south-westerly winds predominating for the rest of the time), it would still break the trend. Even a smaller winter 1995/96-type snow event would.

For those of you that believe that that a warm September/Cold October increases the chances of a warmer than average winter, read the previous winter thread, it clearly shows a slight bias towards cold.

A warm September and then a cold October has historically been the harbinger of a cooler than normal winter for the UK? Where do you get this evidence from?

To be fair the closest evidence I have seen does not back up my assertion of "a cooler and wetter than average September + a warmer and drier than average October = a winter on the cool or colder side of average" either, but that the results are more "inconclusive" than anything else. As a small aside, I think this is also more so for September and November. Ask Kevin Bradshaw (Mr_Data) if you want the figures.

Some strange conclusions but insightful as always.

Edited September 18, 2006 by Damien

[viking_smb]

so lads is it going to snow this year like dec 2005 cos i want to play with the car on stanwell crescent ( cardiff lads will know where it is, penarth) as the unit is by there and it is a very steep road and i want to try the unit minibus (LDV convoy 17 seater 2.6 TD with towbar) on the snow

rob

[Damien]

so lads is it going to snow this year like dec 2005 cos i want to play with the car on stanwell crescent

What snow in December 2005?

What snow in winter 2005/06?

What a waste of a winter in the return of BritPop years - boring and snowless. Yuk.

[summer blizzard]

***ECPC dynamic winter forecast***

If you remember a few weeks ago we were discussing the very interesting if very questionable ECPC output with that phenomenal chart showing most of the Northern Hemisphere as below normal for the coming December:

complete with a nice easterly "warm (or rather in this case "warmer") patch" type set-up just above the UK in the G-I-N corridor.

I've not yet seen the current ECPC "short-range" charts (which would now go into early January BTW), but I was hoping that the ECPC "dynamic" would back up their current forecast of serious cold for the NH in December. And it does... ... of sorts:

These charts show a well above normal November and December (or a O-N-D and N-D-J period to be more exact) but a slightly above average or close to normal January and February (D-J-F and J-F-M period respectively). So a 2000/01-type winter possibly from that, only with January slightly cooler than December minus GW. A mild end to 2006 as a year though for most of us. A colder than average winter beginning in November for the Eastern United States... again. A small El Niño too.

It should also be noted that the southern tip of Greenland is above normal... again. This is an interesting point to note as far as the Jet stream is concerned.

These charts have consistently shown a mild winter for some months now, and now - at this critical moment in this critical month for winter - they are showing a more "normal" or "slightly above average" winter.

Overall I would say that those charts show what is closer to a slightly over average than normal winter due to Western and even Central Europe being also slightly above average, the cold (which is in itself not that intense this year looking at those charts albeit just slightly below average for those regions nonetheless) never really leaving Eastern Europe, esp. the ancient Muscovy region.

Or even 1990/91, which was also a recent (in meteorological terms) "weakly positive" NAO winter.

Overall, i would say that the November and December charts show the Azores High just to the west of the British Isles with mild northerlies as in 2004, however January and February look rather unsettled however with a fairly southerly tracking Jet Stream we may see several northerlies and easterlies with an abundance of snow at times.